I have not read thru the entire thread. It's very possible I'm repeating another's recommendation.
Check out Pakt. I've used the Pakt One Travel Duffle (35L) on several international trips up to 11 days at a time. Love it. Roomy enough to carry just about all I need for a week-long (or longer) trip; small/soft enough to fit into small overhead bins; designed to make all items easy to pack as well as access; sturdy & durable materials.
Not suggesting you select that bag, of course; just sharing my experience based on how well designed their gear is.
Their Everyday 15L Bag may suit you:
https://paktbags.com/products/everyday-15l